This application claims the priority of Korean Patent Application Nos. 2002-49426 and 2003-22218 filed on Aug. 21, 2002 and Apr. 9, 2003, respectively, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.
1. Field of the Invention
The present invention relates to small sized heat transferring device, and more particularly, to a substantially flat heat transferring device for cooling high heat-generating chips.
2. Description of the Related Art
Due to the rapid development in semiconductor techniques and methods of manufacturing semiconductor devices, ultra-slim electronic devices (e.g., laptop computers), which show much greater performance having smaller thickness and volume, have become widely used.
In such ultra slim electronic devices, it is very important to cool high heat-generating elements having a higher calorific power, such as a CPU chip installed in a computer, as well as the entire device. Most of the high heat-generating elements in an electronic device are considered important to the operation of the entire device. Specifically, unless heat generated from such high heat-generating elements is removed as soon as possible, the functions of the high heat-generating elements may be considerably degraded. In an even worse case, the heat-generating elements may be damaged, in which case the entire device may not operate at all.
In recent years, with an increasing awareness of how important cooling of high heat-generating elements is, various coolers for cooling high heat-generating elements have been suggested.
FIGS. 1 through 3 are cross-sectional views of conventional cylindrical heat pipes. In particular, FIG. 1 shows a cylindrical heat pipe 10 inside of which a groove 12 is formed. FIG. 2 shows a cylindrical heat pipe 20 inside of which a sintered metal 22 is provided. FIG. 3 shows a cylindrical heat pipe 30 inside of which a mesh screen 32 is provided.
Referring to FIG. 1, vapor, which is vaporized by heat generated from a heat source (not shown), is transferred to a condensing part (not shown) via a hollow 14 in the heat pipe 10. A liquid-phase coolant provided from the condensing part is fed back to a vaporization part (not shown) through the groove 12.
Hollows 24 and 34 shown in FIGS. 2 and 3, respectively, have the same function as the hollow 14 shown in FIG. 1. In addition, the sintered metal 22 and the mesh screen 32 shown in FIGS. 2 and 3, respectively, correspond to the groove 12 shown in FIG. 1 in terms of function.
As shown in FIG. 4, a vaporization part 44 is located at one end of a cylindrical heat pipe 40 to contact a heat source, and a condensing part 48 for compressing vapor is located at the other end of the cylindrical heat pipe 40. Reference numeral 46 represents a vapor pathway which is connected between the vaporization part 44 and the condensing part 48. Arrows in the heat pipe 40 represent the direction of the movement of a coolant. Vapor entering the condensing part 48 through the vapor pathway 46 changes into a liquid-phase coolant. The liquid-phase coolant permeates a porous material 42 provided inside the heat pipe 40 and moves to the vaporization part 44 due to capillary action in the porous material 42. The cylindrical heat pipes shown in FIGS. 1 through 3 include the groove 12, the sintered metal 22, and the mesh screen 32, respectively, instead of the porous material 42.
The cylindrical heat pipes shown in FIGS. 1 through 3 can be used for ultra slim electronic devices (e.g., laptop computers), but the heat pipes must be pressed to have a smaller thickness and must be bent to increase the area of heat transmission of a fan in the condensing part 48.
However, it is hard to bend a heat pipe pressed to have such a small thickness, and even if the heat pipe can be bent, capillary means provided inside of the heat pipe are physically deformed by the bending, therefore downgrading the performance of the heat pipe.
Additionally, a wick structure provided inside each of the cylindrical heat pipes shown in FIGS. 1 through 3 can be applied to an ultra slim heat pipe. However, in the case of applying the groove 12 shown in FIG. 1 to such an ultra slim heat pipe, the manufacturing costs of the heat pipe increase because it is very difficult to form a fine groove in an ultra slim heat pipe. Alternatively, if the sintered metal 22 shown in FIG. 2 or the mesh screen 32 shown in FIG. 3 is applied to the wick structure of an ultra slim heat pipe, the decrease in flow pressure becomes greater (because the wick layer gets thinner). In addition, because the size of pores is irregular, the surface tension of a coolant weakens. Thus, the cooling efficiency of the heat pipe is lowered.